$24 FLYING FOXES of the vertebrae tend to become ankylosed in old individuals ; the caudals have no processes, but are like those quite at the end of the series in long-tailed animals. The sternum is keeled for the better attachment of the pectoral muscles, the chief muscles of flight. The ribs, which are much flattened, are occasionally ankylosed together by their margins. There i& a well-developed clavicle. In the carpus the scaphoid, lunar, and cuneiform are all fused together. In the hind-limb the fibula is rarely fully developed. The Bats are divisible into two primary groups, which are those of the Megachiroptera and the Microchiroptera. SUB-ORDER 1. MEGACHIROPTERA. The Pteropodidae are frugivorous Bats, usually of large size. The chief distinguishing feature is the fact that the molars are not tubercular, but marked . with a longitudinal furrow, which is, however, concealed in the genus Pteralopex by cusps. The palate is continued back behind the molars. The index finger has three phalanges, and is usually clawed. The ears Fro. 256.—Sktill of Pteropus fuscus. x f. (After de Blainville.) are oval, and the two edges are in contact at the base of the ear. The tail, if present, has nothing to do with the inter- fetnoral membrane. This group is entirely Old "World in range. The genus Pt&ropus embraces the creatures known as Flying Poxes. They are the largest forms in the sub-order, sometimes having an expanse of wing of 5 feet (this is the case with P. edidis). The muzzle is long, and the face therefore ff foxy " in appearance.